FYI - That bumper was sold by a company called "Animal4x4" that is no longer in business.
I've looked everywhere for the plans, but whoever has them isn't letting them out into the world. The last I heard, "Mr. Z" (the forum founder of zr2usa.com) has the plans, but I haven't seen anywhere that you can purchase it, whether it's bolt-on or a weld-able kit.